BY R. VON LENDENFELD, PH.D. 295 



penicillate. The inhaleut canals, whether ramifying or not, always 

 taper slightly centripetally and become very regularly cylindrical 

 towai'ds the blind end. These canals are nearly straight and 

 attain a length of 1 — 2 mm. 



A.S mentioned above, the sponge-tissue, which divides the system 

 of these inhalent canals from the exhalent ones, is but a very thin 

 membrane, measuring only 0-016 mm. on an average in diameter; 

 except whei'e a main fibre intervenes. (Plate XXVII., fig. 7, H.) 

 Divided from the parallel and straight inhalent canals by this 

 membrane we find the exhalent canals, which are wider, measur- 

 ing on an average 0-12 mm. in diameter, cylindrical and likewise, 

 mostly straight and tending upward. These are oval or circular 

 in transverse section. (1). (Plate XXVII., fig. 7, e.) Small 

 canals, as some in this figure, are rare. 



The exhalent canals unite in a penicillate manner, they are 

 slightly more ramified than the inhalents, and finally open into a 

 large and irregular central cavity, the oscular tube. (Plate 

 XXVII., fig. 7, A ; Plate XXIX., fig. 12, 0.) Also this, like all 

 the other canals, tends upwards and genei'ally measures about 

 O'i X l'5mm. in diametei', on an average it attains a length of 

 2 — 3 mm. The osculum is circular, and measures about 3 mm. 

 in diameter, so that the oscular tube appears constricted at its 

 termination. No oscula are found on the external surface. The 

 osculum lies at the same level as the surface around, it is not 

 raised above it. 



The ciliated chambers (Plate XXVIIL, fig. 11., Plate XXIX., 

 fig. 13), fill the whole of the membrane between the canal systems 

 as described above in the genus diagnosis. They form one con- 

 tinuous, dense and uninterrupted layer. Filling the whole thickness 

 of it, they measure 0-016 in diameter, and are accordingly quite 

 exceptionally small. They are perfectly spherical. 



(1) On the section these canals appear oval, but I think that this is due 

 to shrinking and pressure during the complicated method of hardening, itc. 

 I believe that in life the whole structure must be more loose, and all 

 cavities more rounded and larger than in hardened specimens. 

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